Fingerprint authentication apparatus

ABSTRACT

A fingerprint authentication apparatus has a combined visible/infrared light source, which illuminates a finger placed on an optical image sensor with both infrared light and visible light. The optical image sensor has a block with infrared sensitivity and a block within infrared sensitivity, and generates a fingerprint image from light scattered by the finger. The infrared sensitivity of the infrared-sensitive block of the optical image sensor is such that a clear image is obtained from a living organism, and an unclear image is obtained from a replica. If the finger is an actual living finger, the fingerprint images from both blocks are clear, but in the case of a replica, the image from the block having infrared sensitivity is clear, and the image from the block without having infrared sensitivity is unclear. A reference processing section compares the clarity of the fingerprint images from the block with infrared sensitivity and the block without having infrared sensitivity, and if there is a difference therebetween, judges that the finger was a replica. After this is done, an image processing section  14  extracts minutiae from the fingerprint image, and a comparison section compares the fingerprint data with fingerprint in a database.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical fingerprint authenticationapparatus.

2. Related Art

Because one cost of today's widespread information system includingmaking use of computers is the risk of leakage of confidential andprivate information and the danger of unauthorized access toconfidential areas, there is an urgent need in our information-intensivesociety for identification and authorization of individuals.

Approaches to this problem are, for example, the input of a personalidentification number (PIN) when using a cash card in an automaticteller machine of a bank, and the mandatory reading of an authorizationcard and input of a password when entering a computer room. However,with cards being used for a broad spectrum of functions, the managementof cards held by individuals has become troublesome.

Additionally, individuals forget their PINs or passwords, and there is adanger that these will be leaked to or read by others.

The fingerprint has long been thought of as a good alternative to PINsand passwords as a means for individual authentication. The fingerprintcan be thought of as high-level identification information, andidentification information which, of course, the individual is notrequired to memorize or recall.

In a general fingerprint comparison apparatus, when a fingerprint isinput using an image sensor, a recognition section performs imageprocessing of the fingerprint, and detects characteristic points of thefingerprint, these being known as minutiae.

The similarity of the input fingerprint with a fingerprint in a databaseis calculated from the minutiae.

This similarity is represented by a value known as a score, the higherbeing the score, the greater being the similarity of the inputfingerprint with a fingerprint in the database. If the score exceeds aprescribed threshold value, the input fingerprint is judged to be thesame as the fingerprint stored in the database.

In a fingerprint identification apparatus as described above, however,it is not possible to distinguish between the fingerprint of an actualliving person and a replica thereof (that is, a copy of a fingerprintcreated in a non-living medium).

For this reason, in a case in which it is possible to obtain a precisephotograph of a fingerprint of a living person, for example, there is adanger that if this were to be input in place of an actual livingfingerprint, the apparatus would erroneously recognize it as an actualliving fingerprint.

In the past, various proposals have been made to avoid the above-notedproblem. For example, in Japanese patent No. 2554667, directed at an“individual authentication apparatus” (hereinafter referred to as priorart example 1), the apparatus has means for measuring the temperature atthe location of the living body at which the authentication is to bedone (specifically, a thermocouple disposed in the fingerprint readingsection), means for judging whether or not the measured temperature iswithin a pre-established body temperature range (30° C. to 38° C.), andmeans for performing a comparison for authentication only in the case inwhich the result of the judgment was that the measured temperature waswithin the pre-established range.

According to this technology, it is possible to achieve an individualauthentication apparatus that does not recognize a fingerprint taken,for example from a photograph or a cut-off finger, that is, from alocation other than a part of the actual body of the person to beauthenticated.

Furthermore, this apparatus uses a contact-type method, in which afinger is brought into contact with a fingerprint reading section andthe fingerprint is read.

In the Japanese unexamined patent publication (KOKAI) No.11-235452,directed at a “Lock opening apparatus with an identification function”(hereinafter referred to as the prior art example 2), there is languagedescribing an optical fingerprint comparison apparatus for use as asecurity measure for an amusement location.

This optical fingerprint comparison apparatus shines illumination onto afingerprint part of a finger brought into contact with a prism, thereflected light therefrom being guided to an image sensor, and thefingerprint pattern being detected therefrom.

This apparatus has means for making a fingerprint comparison betweenpriorly stored fingerprint data and the fingerprint pattern pressed upagainst the prism, means for performing finger recognition, and alock-opening means for opening a lock mechanism only when there is bothcoincidence resulting from the comparison by the fingerprint comparisonmeans and finger identification by the finger identification means.

The finger identification means can be body temperature, pulse,fingernails and skin, and the shape of the finger.

Additionally, in the Japanese unexamined patent publication (KOKAI)No.10-187954, directed at a “All-in-one fingerprint reading system witha heating resistor” (hereinafter referred to as prior art example 3).

In contrast to the above-described contact-type system, in which thefingerprint reading means is separated from the means for measuring thetemperature of the body part, the system of the Japanese unexaminedpatent publication (KOKAI) No.10-18795 combines these two elements. Thatis, a fingerprint reading sensor, up against which the finger ispressed, has an active surface of an element that is highly responsiveto changes in temperature, and a built-in heating resistor for bringingabout a transient temperature change in the sensitive element.

The thermal change caused by the heating resistor results in anelectrical signal that differs, depending upon the thermal conductivitybetween the grooves and the raised portions of the lines of afingerprint in contact with the sensing element matrix.

Fingerprint recognition is performed based on the above, and it ispossible to recognize whether or not the fingerprint is from part of anactual living person during the fingerprint reading, via thecharacteristic heat released from a finger.

In the above-described prior art example 1, however, a thermocouple isused to detect the temperature of the object under measurement, andbecause a judgment is made that the object is an actual person if thetemperature is within a prescribed temperature range (30° C. to 38° C.),if a fingerprint replica is raised to within the prescribed temperature,an erroneous judgment that the object is a human body will be made,thereby not solving the problem.

In the prior art example 2, a fingerprint pattern is recognized by animage sensor 106 using a non-contact method, and a detector 101 detectsbody temperature, pulse, or the like. In the case of body temperaturedetection, in the same manner as in the prior art example 1, it ispossible to defeat this apparatus by simply warming up a replica.

In the case of pulse detection, the need to have quite a sensitivesensor to measure the pulse makes this device impractical. Additionally,even if such as device were achieved, the auxiliary detector (pulsedetector) would become much more expensive than the image sensor, whichis the main sensor, this also making the device impractical.

In the prior art example 3, the fingerprint reading section and the bodytemperature detector are combined as one. However, because of the use ofan element sensitive to changes in temperature as the sensor that readsthe fingerprint, this system is susceptible to changes in ambienttemperature, making it necessary, for example, to change the thresholdvalue between the summer and the winter, this presenting a problem interms of maintenance.

Accordingly, it is an object of the present invention to solve theabove-noted problems encountered the prior art, by providing stablefingerprint authentication, which is little influenced by the ambienttemperature.

Another object of the present invention is to provide a fingerprintauthentication apparatus that is maintenance free.

SUMMARY OF THE INVENTION

To achieve the above-noted objects, the present invention adopts thefollowing described basic technical constitution.

Specifically, a first aspect of the present invention is a fingerprintauthentication apparatus having an imaging section, which images theobject of fingerprint authentication using an optical image sensorhaving sensitivity in the infrared region, an image processing section,which performs image processing of data obtained from the imagingsection, thereby obtaining a fingerprint image, and a comparisonsection, which performs a comparison of the thus-obtained fingerprintwith a priorly stored fingerprint image.

A second aspect of the present invention is a fingerprint authenticationapparatus having an imaging section which forms an image of afingerprint to be authenticated by an optical image sensor formed by afirst optical image sensor having sensitivity in the infrared region anda second optical image sensor having sensitivity in the visible lightregion, first and second optical image sensors being mutuallyneighboring, an image processing section, which processes the dataobtained from the image processing section and obtains a fingerprintimage therefrom, and a comparison section, which performs a comparisonof the fingerprint image to be authenticated thus obtained with apriorly stored fingerprint.

More specifically, the optical image sensor of the present invention isa CCD or CMOS device, and in the optical image sensor or block withinfrared sensitivity used in the present invention a deep P-wellstructure is formed directly beneath an N channel, and between a Psubstrate and an N channel, this having a lower concentration andgreater depth than those of the normal P-well.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing showing the configuration of a first embodiment of afingerprint authentication apparatus according to the present invention.

FIG. 2 is a drawing showing the configuration of a second embodiment ofa fingerprint authentication apparatus according to the presentinvention.

FIG. 3 is a drawing showing the configuration of a third embodiment of afingerprint authentication apparatus according to the present invention.

FIG. 4 is a drawing showing the configuration of a fourth embodiment ofa fingerprint authentication apparatus according to the presentinvention.

FIG. 5 is a schematic representation illustrating judgment of a livingfingerprint and a replica using an optical image sensor in the third andfourth embodiments of the present invention.

FIG. 6 is a cross-sectional view showing the structure of image sensors,(A) showing the structure of an image sensor having no infraredsensitivity, and (B) showing the structure of an image sensor havinginfrared sensitivity.

FIG. 7 is a circuit diagram showing an element of a general opticalimage sensor.

FIG. 8 is a flowchart illustrating the first and second embodiments of afingerprint authentication apparatus according to the present invention.

FIG. 9 is a flowchart illustrating the third and fourth embodiments of afingerprint authentication apparatus according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of a fingerprint authentication apparatus according to thepresent invention are described in detail below, with references made torelevant accompanying drawings.

The present invention acquires an image of an object (finger) using anoptical image sensor having infrared sensitivity to sense lightscattered or reflected from the object, and in doing so acquires animage (fingerprint pattern) of the object, determines the claritythereof, and performs a judgment as to whether the pattern is livingfingerprint (of a person) or a non-living fingerprint (replica).

If the result of this judgment is that the fingerprint is a livingfingerprint, a comparison is made of the obtained pattern with a priorlystored image, and a judgment is made as to whether the fingerprint isthat of a particular individual.

The present invention uses a CCD or a CMOS device as a two-dimensionaloptical image sensor having infrared sensitivity, the object having beenimaged by being illuminated with infrared light and an image beingobtained therefrom, a clear fingerprint image being obtained in the caseof a living fingerprint, but a clear image not being obtained in thecase of a replica.

The present invention is based upon these experimental results.

In the present invention, Rubber, plastic, or asbestos or the like areused as replica materials. The reason for using these materials is thatthe simplest method of forming a replica of a fingerprint is to firstmake a cast of the finger and then pour the material into the cast,which serves as a mold.

Although the reason for this phenomenon has not at this point in timebeen explained at the present time, its repeatability is supported byexperimental results.

Various embodiments of the present invention are described below.

FIG. 1 is a drawing showing the configuration of a first embodiment of afingerprint authentication apparatus according to the present invention.

This embodiment is an optical fingerprint authentication apparatushaving a prism 18 and a lens 19.

A feature of this embodiment is the use of an infrared light source 12and an optical image sensor 13 having infrared sensitivity.

It is worthy to note that the above-noted effect is achieved without theuse in addition to the optical image sensor 13 of a means foridentifying a living organism, such as a means for detecting bodytemperature.

This is possible because this means is integratedly built into theinfrared light source 12 and the optical image sensor 13.

The optical image sensor 13 with infrared sensitivity will be explainedhereunder.

Note that it has characteristic in that it responds to infrared light,producing a clear image in the case of a living organism and annon-clear image in the case of a replica.

In general, as is widely known, an optical image sensor is formed by amultitude of elements, each formed by a photodiode and an associatedamplifier and being arranged in a matrixed configuration, as shown inFIG. 7.

More specifically, when light from the light source strikes aphotodiode, the photodiode generates an electrical current proportionalto the incident light. This electrical current is amplified by theamplifier and extracted, resulting in an electrical signal correspondingto the light. To form a matrix of elements configured in this manner,the activated terminals of the amplifiers are connected to thehorizontal lines HL of the matrix, and the outputs of the amplifiers areconnected to the vertical lines VL of the matrix.

FIG. 6 is a cross-sectional view showing the semiconductor devicestructure in elements of image sensors, FIG. 6(A) showing the structurein an element of an optical image sensor without having infraredsensitivity and FIG. 6(B) showing the structure in the optical imagesensor 13 having infrared sensitivity.

In an optical image sensor without having infrared sensitivity whichforming the photodiode between the P-substrate and N-channel N, there ismerely a shallow P-well layer, as shown in FIG. 6(A),

In contrast to the above, in the optical image sensor 13 with havinginfrared sensitivity forming the photodiode, as shown in FIG. 6(B),between the P-substrate and the N-channel N, there is a deep P-well.

This deep P-well has a lower concentration than that of a usual P-well,and is formed as a deeper layer than that thereof, this being formeddirectly below the N-channel.

As a result, the usual P-well is formed only over the deep P-well onboth sides, and directly below the N-channel layer.

Because infrared light generates an electrical charge at a deeperlocation in a semiconductor device than visible light, it is possibleusing a deep P-well structure to augment the electrical charge generatedat a deep location.

Therefore, an optical image sensor 13 having a deep P-well structure hassensitivity in the infrared region. In the above description, theexample is that of a CCD image sensor.

A person skilled in the art, however, will understand that this appliesas well to a CMOS optical image sensor.

The operation of the first embodiment is described below, with referencemade to the flowchart of FIG. 8.

When performing fingerprint authentication, in response to aninstruction from a host device (not shown in the drawing), a controller11 irradiates the infrared light from the infrared light source 12 tothe prism 18.

When this is done, the object being authenticated (finger 10 of a livinghuman, in the normal case) is placed over the prism 18.

Infrared light incident to the prism 18 is reflected at the surface atwhich the finger 10 makes contact with the surface of the prism 18,collected by the lens 19, and input to the optical image sensor 13. Theoptical image sensor 13 converts the infrared light incident thereto toan electrical signal, which is input to the image processing section 14.

The image processing section 14 performs image processing of the currentinput from the optical image sensor 13, under the control of thecontroller 11 (step S1 in FIG. 8).

When this is done, by virtue of the above-described infraredcharacteristics, from the light reflected by the “finger” a clear imageof the finger print is obtained in the case of an actual living finger,but a non-clear image thereof is obtained in the case of a replica of afinger.

The image processing section 14 detects minutiae from the thus obtainedimage (step S2 in FIG. 8), and performs a judgment as to whether or notthe number thereof is equal to or greater than a prescribed number (FIG.S3 in FIG. 8).

If the result is that the number of minutiae is less than the prescribedamount, authentication is not possible.

If, however, the minutiae count is equal to or greater than theprescribed number, the comparison section 15 performs a fingerprintcomparison (step S4 in FIG. 8).

In performing this fingerprint comparison, a comparison is made betweenimage data of the input fingerprint and image data of a fingerprintpriorly stored in the database 16 and a similarity therebetween iscalculated from the minutiae, this similarity being expressed as a valueknown as the score.

A judgment is made as to whether or not the score is equal to or greaterthan a threshold value (step S5 in FIG. 8).

If the result of this judgment is that the score is equal to or greaterthan the threshold value, a judgment is made that the fingerprint isthat of an authorized person, while, if the result of this judgment isthat the score is less than the threshold value, a judgment is made thatthe fingerprint is not that of an authorized person.

Because this embodiment can be easily achieved by replacing the visiblelight source of a fingerprint authentication apparatus of the past withan infrared light source, and replacing the optical image sensor of afingerprint authentication apparatus of the past with an optical imagesensor having infrared sensitivity, it is possible to achieve thisembodiment as a modification of an existing apparatus.

FIG. 2 is a drawing showing the configuration of a second embodiment ofa fingerprint authentication apparatus according to the presentinvention. In this fingerprint authentication apparatus, rather thanusing a prism and lens or such optical components, and in contrast to anoptical fingerprint authentication apparatus in which a finger isbrought into direct contact with an optical image sensor, an infraredlight source 22 and an optical image sensor 23 having the infraredsensitivity are used, similar to the case of the first embodiment.

Specifically, in this apparatus, the finger is directly illuminated, thescattered light therefrom being received by a two-dimensional imagesensor formed by a multitude of light-receiving elements arranged in atwo-dimensional pattern.

When a fingerprint is input, the fingerprint is brought into proximalcontact with a light-receiving surface of the light receiving elements.

The light-receiving elements having light-receiving surfaces being inproximal contact with raised parts of the fingerprint, detects a brightregion to which the scattered light from inside the finger tip, can bereached in a good condition through the raised parts of the fingerprint,as raised parts of the fingerprint.

In contrast to this, light-receiving elements having light-receivingsurfaces in proximal contact with valley parts of the fingerprint,detects non-bright region to which the scattered light from inside thefinger tip cannot be reached, as valley parts of the fingerprint.

In FIG. 2, the infrared light source 22 and the optical image sensor 23are configured as described above.

When a fingerprint comparison is being done, the finger 20 is broughtinto direct contact with the optical image sensor 23.

Infrared light illumination from the infrared light source 22 isscattered by the finger 20, this scattered light being received by theoptical image sensor 23.

Subsequent processing is the same as the processing in the case of thefirst embodiment, and the flowchart of FIG. 8 applies in this case aswell.

In FIG. 2 and FIG. 1, the lower-order digit of the reference numeralsbeing the same indicates that these are corresponding elements of thetwo embodiments.

FIG. 3 is a drawing showing the configuration of a fingerprintauthentication apparatus according to the third embodiment.

In this embodiment, which is a fingerprint authentication apparatususing a prism 38 and a lens 39, the use of an optical image sensor 33having infrared sensitivity is in common with the first embodiment shownin FIG. 1.

However, this embodiment uses a combined visible/infrared light source32, in which visible light is mixed with infrared light is used, andconsideration is given to the optical image sensor 33, an accompanyingreference processing section 37 is further provided.

The optical image sensor 33 is formed by a block having infraredsensitivity and a block without having infrared sensitivity.

Each one of the former and the latter forms the semiconductor deviceconfigurations as shown in FIG. 6(B) and FIG. 6(A), respectively.

In the case in which the optical image sensor 33 is implemented on asingle chip, with this separation into blocks, both blocks reside on oneand the same chip.

Alternately, it is possible to implement the optical image sensor 33with a chip having infrared sensitivity and a chip without havinginfrared sensitivity, this method resulting in an improved chip yield.

Additionally, an alternative simplified method is that of partiallyaffixing a infrared-cutting filter to an optical image sensor havinginfrared sensitivity, thereby forming a block that does not haveinfrared sensitivity in the portion having the infrared-cutting filter.

FIG. 5 is a drawing illustrating the discrimination between a livingorganism and a replica in the optical image sensor 33, the upper part ofwhich shows the block having infrared sensitivity, and the lower part ofwhich shows the block without having infrared sensitivity.

As shown in FIG. 5(A), in the case in which a finger to fingerprintauthenticated is placed on the optical image sensor 33, if the finger isan actual living finger, because the image obtained from the opticalimage sensor 33, as shown in FIG. 5(B), because of the infraredsensitivity as shown in the upper part of the drawing, is a clearfingerprint image, and although the bottom part does not have infraredsensitivity, the visible light sensitivity in this region results in aclear fingerprint image.

In the case in which the “finger” was in fact a replica, the imageobtained from the optical image sensor 33, as shown in FIG. 5(C),because of the infrared sensitivity in the upper part of the opticalimage sensor 33, is an unclear fingerprint image, and although there isno infrared sensitivity in the lower part, a clear fingerprint imageresults.

The reference processing section 37 makes a comparison between theclarity of the input fingerprint images between the block with infraredsensitivity and the block without having infrared sensitivity.

As is clear from FIG. 5, in the case of the finger of a living organism,there is no difference in clarity between the images obtained by the twoblocks, but in the case of a replica, there is a difference in theclarity between the images obtained by the two blocks. Using this, it ispossible to distinguish between a living finger and a replica.

Although for simplicity of description in FIG. 5 the example shown isthat in which the optical image sensor 33 is divided into two blocks, itis also possible to divide this optical image sensor 33 into a greaternumber of blocks, in which case, the blocks having infrared sensitivityand the blocks not having infrared sensitivity can be disposed in acheckerboard pattern.

The finer is the separation into blocks, the closer is the part of thefingerprint image to be compared by the reference processing section 37,thereby enabling a more precise comparison.

The ideal arrangement is one in which a block with infrared sensitivityand a block without having infrared sensitivity are disposed for eachline of the optical image sensor 33. Additionally, division into blocksis possible not only in the horizontal direction, as shown in FIG. 5,but also in the vertical direction.

FIG. 9 is a processing flowchart of processing performed in the secondembodiment, in which a “Clarity difference within prescribed range?”step T1 is inserted before the step S1 of FIG. 8. If the result of thecheck performed at step T1 is affirmative, the processing of steps T2and thereafter is performed. In FIG. 9, steps T2 through T6 correspondto steps S1 to S5 of FIG. 8.

The following methods can be envisioned as a specific method of imagecomparison between the blocks in the reference processing section 37,such a method being performed by, for example, a DSP (digital signalprocessor) within the reference processing section 37.

The first method is that of performing a Fourier transform of theclarity of each of the blocks with regard to the input fingerprintimage.

In the Fourier transform in this case, the transition density of thebright parts and the dark parts of the fingerprint image is converted tospatial frequency, the parts having a high transition density having ahigh spatial frequency, and the parts having a low transition densityhaving a low spatial frequency.

In the case of a living organism fingerprint, because clear images areobtained from both the block with infrared sensitivity and the blockwithout having infrared sensitivity, as shown in FIG. 5(B), the spatialfrequency for both blocks is high, and there is no different between thespatial frequencies.

In the case of a replica, however, as shown in FIG. 5(C), because theblock having infrared sensitivity yields an unclear image, itscorresponding spatial frequency is low, and because image yielded fromthe block without having infrared sensitivity is clear, itscorresponding spatial frequency is high, so that there is a differencebetween the spatial frequencies, this difference enabling elimination ofthe replica.

A second specific method of image comparison is that in which thestandard deviation of the clarity from each of the blocks with regard tothe input fingerprint image is calculated. In the case of imaging areplica, because the image from the block having infrared sensitivity isunclear, the standard deviation of this clarity is smaller than that ofthe clarity of the image from the block without having infraredsensitivity.

In the case of a fingerprint from a living organism, there is nodifference between the standard deviation of the blocks.

In the case of a replica, however, the standard deviation for the blockwith infrared sensitivity is low compared with the standard deviationfor the block without having infrared sensitivity, this fact being usedto eliminate a replica.

A difference in the absolute values of the sensitivity between the blockwith infrared sensitivity and the block without having infraredsensitivity occurs. Because of this, a controller 31 sets the shutterspeed for each of the blocks independently, so as to obtain properimages.

The above-noted shutter speed is the time in a PN junction of theoptical image sensor 33 from the application of a reset to the N-channellayer, which starts the reading of the current signal, until thecompletion of readout, the shutter speed of a block having a highinfrared sensitivity being set so as to be faster than the shutter speedof a block without having infrared sensitivity. As a result, theexposure time of a block with high infrared sensitivity is shorter thanthat of a block without having infrared sensitivity, therebycompensating for the difference in sensitivity, and achieving an overallimage having the same brightness for both blocks.

The controller 31 can achieve the same effect by appropriate sensorsensitivity settings independently for each block. Specifically, thecurrent amplification factor of an amplifier in the optical image sensor33 with respect to a block having infrared sensitivity is set lower thanthat of an amplifier for a block without having infrared sensitivity.

Additionally, in the case in which it is difficult for the controller 31to simultaneously set different shutter speeds for two blocks, as notedabove, it is alternatively possible for the controller 31 to detect anappropriate shutter speed for each of the blocks and, after imaging ateach of the shutter speeds with a time shift therebetween, to synthesizean image from the images of the individual blocks. This can also beapplied in a case in which the amplification factors for the two blocksare set differently.

FIG. 4 is a drawing showing the configuration of an optical fingerprintauthentication apparatus according to the fourth embodiment of thepresent invention. In this embodiment, rather than using a prism andlens or such optical components, the finger is brought into directcontact with an optical image sensor, the relationship between thisfourth embodiment and the third embodiment being the same as therelationship between the second embodiment and the first embodiment.

Specifically, in this fingerprint authentication apparatus, a combinedinfrared/visible light source 42 providing illumination with mixedinfrared light and visible light being used and consideration beinggiven to the optical image sensor 43, an accompanying referenceprocessing section 47 being further provided.

The optical image sensor optical image sensor 43 is formed by a blockhaving infrared sensitivity and a block without having infraredsensitivity. A reference processing section 47 performs a comparison ofthe clarity of the fingerprint images input between the block withinfrared sensitivity and the block without having infrared sensitivitywithin the optical image sensor 43.

Infrared light illumination from the visible/infrared infrared lightsource 42 is scattered by a finger is scattered by a finger 40, andreceived by the optical image sensor 43. Subsequent processing is thesame as described with regard to the third embodiment, and the flowchartof FIG. 9 applies in this case as well. In FIG. 4 and FIG. 3, thelower-order digit of the reference numerals being the same indicatesthat these are corresponding elements of the two embodiments.

By adopting the technical constitutions described in detail above, thepresent invention achieves a number of effects. The first effect is thatof, without using the piezoelectric effect and/or pyroelectric effect asin the past to read a fingerprint image, reading the image with anoptical image sensor having infrared sensitivity, resulting in a stablefingerprint authentication apparatus that is little affected by theambient temperature.

The second effect achieved by the present invention is made possible byperforming stable fingerprint authentication with little influence fromthe ambient temperature, thereby reducing the maintenance burden in afingerprint authentication apparatus according to the present invention.

1. A fingerprint authentication apparatus comprising: an imaging sectioncomprising a first optical image sensor having infrared sensitivity anda second optical image sensor having sensitivity in the visible lightregion, said first and second optical image sensors being mutuallyneighboring whereby obtaining an image of an object to be fingerprintauthenticated; an image processing section, which performs imageprocessing of data obtained from said imaging section so as to obtainthe fingerprint image; and a fingerprint comparison section, whichperforms a comparison between said fingerprint image and a priorlystored fingerprint image; wherein a fingerprint image is obtained withsaid object not in contact with said imaging section.
 2. A fingerprintauthentication apparatus according to claim 1, wherein said first andsecond optical image sensors are both selected from a group consistingof a CCD image sensor and a CMOS image sensor, a P-well depth in saidfirst optical image sensor is deeper than that of said second opticalimage sensor, and a concentration thereof is less than that of saidsecond optical image sensor.
 3. A fingerprint authentication apparatusaccording to claim 1, further comprising means for shining infraredlight and visible light onto said object to be fingerprintauthenticated.
 4. A fingerprint authentication apparatus comprising: animaging section comprising a first optical image sensor having infraredsensitivity and a second optical image sensor having sensitivity in thevisible light region, said first and second optical image sensors beingmutually neighboring whereby obtaining an image of an object to befingerprint authenticated; an image processing section, which performsimage processing of data obtained from said imaging section so as toobtain the fingerprint image; and a fingerprint comparison section,which performs a comparison between said fingerprint image and a priorlystored fingerprint image; wherein said first optical image sensors isselected from a group consisting of a CCD image sensor and a CMOS imagesensor each having infrared sensitivity, and wherein said second opticalimage sensor is formed by providing an infrared-cutting filter on saidfirst optical image sensor.
 5. A fingerprint authentication apparatuscomprising: an imaging section comprising a first optical image sensorhaving infrared sensitivity and a second optical image sensor havingsensitivity in the visible light region, said first and second opticalimage sensors being mutually neighboring whereby obtaining an image ofan object to be fingerprint authenticated; an image processing section,which performs image processing of data obtained from said imagingsection as to obtain the fingerprint image; and a fingerprint comparisonsection, which performs a comparison between said fingerprint image anda priorly stored fingerprint image; wherein said first and secondoptical image sensors are both selected from a group consisting of a CCDimage sensor and a CMOS image sensor, a P-well depth in said firstoptical image sensor is deeper than that of said second optical imagesensor, and a concentration thereof is less than that of said secondoptical image sensor.